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  • Analytical Chemistry and Spectroscopy  (3)
  • sarcoplasmic reticulum  (3)
  • 1995-1999  (6)
  • 1
    ISSN: 1573-4919
    Keywords: neonatal rat cardiomyocyte culture ; sarcoplasmic reticulum ; phospholamban ; calcium ATPase ; calcium transport ; thyroid hormone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract This study investigates sarcoplasmic reticulum (SR) calcium-(Ca2+) transport ATPase (SERCA2a) and phospholamban (PLB) in cultured spontaneously contracting neonatal rat cardiomyocytes (CM) to ascertain the function of both SR proteins under various culture conditions. The two major SR proteins were readily detectable in cultured CM by immunofluorescent microscopy using specific anti-SERCA2 and anti-PLB antibodies. Double labeling technique revealed that PLB-positive CM also labeled with anti-SERCA2. Coexpression of SERCA2 and PLB in CM was supported by measurement of cell homogenate oxalate-supported Ca2+ uptake which was completely inhibited by thapsigargin and stimulated by protein kinase A-catalyzed phosphorylation. Under serum-free conditions, incubation of CM with the SERCA2a expression modulator 3,3′,5-triiodo-L-thyronine (100 nM, 72 h) resulted in elevated Ca2+ uptake of +33%. Specific Ca2+ uptake activity was not altered if insulin was omitted from the serum-free culture medium but total SR Ca2+ transport activity was reduced under this culture condition. The results indicate that primary culture of spontaneously contracting neonatal rat CM can be employed as a useful model system for investigating both short- and long-term mechanisms determining the Ca2+ re-uptake function of the SR under defined culture conditions.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-4919
    Keywords: heart ; postnatal development ; sarcoplasmic reticulum ; phospholamban ; calcium transport ; spontaneously hypertensive rats ; growth
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract This comparative study investigates the relationship between sarcoplasmic reticulum (SR) calcium(Ca2+)-ATPase transport activity and phospholamban (PLB) phosphorylation in whole cardiac homogenates of spo`ntaneously hypertensive rats (SHR) and their parent, normotensive Wistar Kyoto (WKY) strain during early postnatal development at days 1, 3, 6, 12 and at day 40 to ascertain any difference in SR Ca2+ handling before the onset of hypertension. At day 1, the rate of homogenate oxalate-supported Ca2+ uptake was significantly higher in SHR than in WKY (0.25 ± 0.02 vs 0.12 ± 0.01 nmoles Ca2+/mg wet ventricular weight/min, respectively; p 〈 0.001). This interstrain difference disappeared with further developmental increase in SR Ca2+ transport. Western Blot analysis and a semiquantitative ELISA did not reveal any difference in the amount of immunoreactive PLB (per mg of total tissue protein) between strains at any of the ages studied. In addition, levels of phosphorylated PLB formed in vitro in the presence of radiolabelled ATP and catalytic (C) subunit of protein kinase A did not differ between SHR and WKY at days 1, 3, 6 and 12. At day 40, C subunit-catalyzed formation of 32P-PLB was reduced by 66% (p 〈 0.001) in SHR when compared to age-matched WKY In the early postnatal period between day 1 and 12 SR Ca2+-transport values were linearly related to the respective 32P-PLB levels of both SHR and WKY rats. The results indicate that cardiac SR of SHR can sequester Ca2+ at a much higher rate immediately after birth compared to WKY rats. The disappearance of this interstrain difference with further development suggests that some endogenous neuroendocrine or nutritional factor(s) from the hypertensive mother may exert an influence upon the developing heart in utero resulting in a transiently advanced maturation of the SR Ca2+ transport function in SHR pups at the time of birth.
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  • 3
    ISSN: 1573-4919
    Keywords: atria ; thyroid hormones ; β-adrenergic effect ; sarcoplasmic reticulum ; phospholamban
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract This paper discusses the mechanisms of two basic effects of thyroid hormones on atrial responses to β-adrenergic agonists, i.e. increased inotropic sensitivity and decreased maximal contractile responsiveness. The increased sensitivity of atria to β-adrenergic agonists under thyroid hormones appears to be related to increases in β-adrenoceptor density and Gs/Gi protein ratio, leading to activation of Gs-mediated pathway, but suppression of Gi-mediated pathway of adenylate cyclase regulation. Therefore, the i/c concentrations of cAMP and corresponding inotropic responses achieve their maximums at lower doses of β-adrenergic agonist. Thyroid hormones also decrease the expression of phospholamban, but increase the expression of sarcoplasmic reticulum Ca+2-pump. As a result, the basal activity of sarcoplasmic reticulum Ca+2-pump increases, but its β-adrenergic activation through phosphorylation of phospholamban decreases. It is suggested that these changes are causal for decreased maximal inotropic and lusitropic responses of atria to β-adrenergic agonists.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 18 (1995), S. 643-646 
    ISSN: 0935-6304
    Keywords: Gas chromatography/Mass spectrometry ; Chiral GC ; Deuterium-labeled compounds ; Hexachlorocyclohexane ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Perdeuterated α-1,2,3,4,5,6-hexachlorocyclohexane (α-PDHCH) was synthesized and isolated in pure form. α-PDHCH was baseline separated from unlabeled α-HCH by high resolution gas chromatography on different stationary phases. α-PDHCH was also resolved into its enantiomeric forms by application of a chiral GC phase. Furthermore, chiral chromatography of a mixture of labeled α-PDHDH and unlabeled α-HCH resulted in four peaks. Standard solutions of α-PDHCH are recommended both as recovery standard for sample clean-up and as internal standard for the quantitation of chlorinated hydrocarbons with GC/MS or GC/ECD in environmental samples.
    Additional Material: 4 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 30 (1995), S. 1562-1566 
    ISSN: 1076-5174
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A simple and rapid method for counting the number of internal disulfide bridges in a protein by incubation with 2-mercaptoethanol and electrospray mass spectrometry analysis of the products was developed. 2-Mercaptoethanol yields intermediate mixed disulfides during reduction of a protein. This results in a molecular weight increase of the protein by 78 Da per disulfide bond, which can easily be determined by electrospray mass spectrometry (ESMS). The number of mercaptoethanol adducts observed by ESMS reveals the number of disulfide bridges in the peptide or protein. Since the protein-mercaptoethanol-disulfide bonds are themselves further reduced by excess mercaptoethanol, the course of the reaction has to be followed in order to detect the maximum number of intermediates. Owing to the volatility of mercaptoethanol, samples can be taken out of the reaction solution for MS analysis without prior purification. Successful experiments were carried out using proteins with one, two, four or six S—S-bonds, covering a mass range from about 1 to over 23 kDa.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 20 (1997), S. 85-93 
    ISSN: 0935-6304
    Keywords: Capillary gas chromatography ; Modified cyclodextrin phases ; Chiral organochlorines ; Biological samples ; Enantiomeric ratios ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Four chiral stationary phases containing modified cyclodextrines diluted in or chemically bonded to a non-chiral phase were used to resolve chiral organochlorine compounds such as α-hexachlorocyclohexane (α-HCH), perdeuterated α-HCH (α-PDHCH), β-and γ-pentachlorocyclohexene (PCCH), oxychlordane, cis-and trans-chlor- dane, cis- and trans-heptachlorepoxide, PCB 95, PCB 132, PCB 149, and Chiral tozaphenes.The elution order was determined by analyzing standards with known enantiomeric excesses.Furthermore, an internal standard was used to even out slight variations in the ratio of peak hights of enantiomers which were determined from injection to injection.None of the chiral stationary phases resolved all chiral organochlorine compounds. However, the β-TBDM(35% heptakis (6-O-t-butyldimethylsilyl-2,3-di-O-methyl)-β-cyclodextrin in OV 1701) column allowed the separation of all compounds under investigation except for PCB 95 and chiral toxaphenes.Emphasis was placed on the separation of as many as possible enantiomers on a chiral phase by application of one temperature program and with respect to unambiguous quantitation of biological samples such as bludder and liver of marine and terrestrial mammals.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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